This invention relates to a vertical beat treating apparatus.
Vertical beat treating apparatuses are known for homogeneously heat treating or thermally diffusing objects to be treated, e.g., semiconductor wafers, to form thin films on the surfaces of the semiconductor wafers.
In such vertical heat treating apparatuses, reaction gases, e.g., NH.sub.3 and SiH.sub.2 Cl.sub.2, are supplied into a reaction vessel which is sealed in an air-tight manner by a cap body, and the reaction vessel is heated up to, e.g., 800.degree. C., by a heater disposed around the outer circumference thereof.
The reaction vessel is loaded with a boat holding semiconductor wafers for heat treatment (i.e., a wafer boat). For the formation of more homogenous SiN films on the surfaces of the wafers, the boat for heat treatment is supported by a rotary shaft which passes through the cap body and is turned by rotary motion of a motor connected to the rotary shaft.
But in the case where a rotation mechanism for the wafer boat for heat treatment is provided in a vertical heat treating device, a problem is encountered in that heat for heating the semiconductor wafers is concentrated on the rotation mechanism for turning the boat, and the rotary shaft thereby possesses a high temperature.
It is also a problem in the case where a magnetic seal member, for example, is used to prevent leakage of reaction gases from between the rotary portion of the rotation mechanism and the cap body, when the magnetic seal member has a temperature above 80.degree. C., oil, for example, containing a magnetic seal material adversely evaporates, with the result that the magnetic seal member is thermally degraded in a rapid manner.
Furthermore, it is also a problem that reaction gases which have leaked through the through-hole in the cap body contact the rotary shaft at high temperatures and corrode it.